1. Field of the Invention
This invention relates to methods of fault prediction and particularly fault prediction methods for electrical distribution systems and monitored loads.
2. Description of the Prior Art
Electrical power has become the most essential commodity of our everyday needs. In manufacturing, where systems like “lean manufacturing” and “just in time” delivery philosophies are pervasive, a reliable and dependable electrical distribution system is more critical to a business's fiscal health than ever before. Unfortunately, global competition has forced production quotas in many companies and industries to increase, while at the same time, forcing many companies to make reductions in their labor force and maintenance budgets as they attempt to reduce operating costs. Such cost savings measures can be expensive. Insurance claims data published in the National Fire Prevention Association (NFPA) publication 70B maintenance standard, shows that almost half of the cost associated with electrical failures could have been prevented. The typical service life of electrical equipment is generally 25-30 years depending on maintenance and upkeep, and much of the aging infrastructure has been in service for 20 years or longer. With electrical distribution systems aging year-by-year, and preventative maintenance programs being cut to improve the corporate bottom line, the likelihood of a facility experiencing a catastrophic failure to its electrical distribution system is increasing.
Another concern for those responsible for the maintenance of electrical systems is that of electrical transients. An electrical transient is a temporary excess of voltage and/or current in an electrical circuit that has been disturbed. Transients are short duration events, typically lasting from a few thousandths of a second (milliseconds) to billionths of a second (nanoseconds), and they are found on all types of electrical, data, and communications circuits. The electrical distribution system and attached load equipment is under constant attack from various types of power line disturbances. The result is an estimated $26 billion-per-year cost to U.S. companies in lost time, equipment repair, and equipment replacement. Transient voltage surges comprise the most severe and immediate danger to sensitive electrical and electronic equipment, and are often a neglected aspect of facility design.
Studies have shown that approximately 80% of transient activity at a given facility may be internally generated. From the normal on-and-off switching of copiers, heating and ventilation, capacitor banks, and air conditioning systems to robotic assembly and welding machines, practically every industrial machine or system causes or is adversely affected by transients. Surges and transient power anomalies are potentially destructive electrical disturbances, the most damaging being over-voltage occurrences and short duration over-voltage events, and the cumulative effect of these transients are a major source of semi-conductor degradation and failure. Thus, a system that can predict electrical faults in enough time to correct them before they cause serious problems is needed.